1. Field of the Invention
The present invention relates to a method of manufacturing an electron source including an activation process.
2. Description of the Related Art
Electron-emitting devices heretofore known are generally grouped into two types: a thermionic emission type and a cold-cathode electron emission type.
Known examples of the cold-cathode electron-emitting devices include, surface conduction electron-emitting devices, field-emission (hereafter referred to as FE-type) devices, and metal-insulating layer-metal (hereafter referred to as MIM-type) devices.
For example, an FE-type device, such as the one disclosed by W. P. Dyke and W. W. Dolan in “Field Emission”, Advance in Electron Physics, 8,89 (1956), or the one disclosed by C. A. Spindt in “Physical Properties of Thin-film Field Emission Cathodes with Molybdenum Cones”, J. Appl. Phys., 47, 5248 (1976), is known.
Also, An MIM-type device, such as the one disclosed by C. A. Mead in “Operation of Tunnel-Emission Devices”, J. Apply. Phys., 32,646 (1961), is known.
An example of the surface conduction electron-emitting device is reported by M. I. Elinson in Radio Eng. Electron Phys., 10, 1290, (1965), and other examples thereof described below are known.
The surface conduction electron-emitting device uses a phenomenon where electrons are emitted when an electric current is allowed to flow in parallel to the surface of a thin film that has a small area and is formed on a substrate. While Elinson proposes the use of an SnO2 thin film for the surface conduction electron-emitting device, the use of an Au thin film (G. Dittmer, Thin Solid Films, 9, 317 (1972)), the use of an In2O3/SnO2 thin film (M. Hartwell and C. G. Fonstad, IEEE Trans. ED Conf., 519 (1975)) and the use of carbon thin film (Hisashi ARAKI, et al.: SHINKU (Vacuum), Vol.26 No.1, p.22(1983)), are also proposed.
According to the above surface conduction type electron-emitting device represented by the device of M. Hartwell et al., generally, energization processing which is called energization forming is performed for the above thin film (conductive thin film) before electron emission to form an electron emitting portion.
That is, in the energization forming, a predetermined direct current voltage, or a direct current voltage which is raised at a very slow rate of, for example, about 1 [V/minute] is applied to both ends of a conductive thin film to supply a current thereto. Thus, the conductive thin film is locally broken, deformed, or altered, thereby forming an electron emitting portion having an electrically high resistance state.
Then, a crack is caused in a portion of the conductive thin film which is locally broken, deformed, or altered. When a suitable voltage is applied to the conductive thin film after the energization forming, electron emission is conducted in the vicinity of the crack.
Also, according to JP 3087849 B made by the present inventor(s), an activation process of a plurality of surface conduction type emitting devices is described in detail as a process for improving the number of electrons to be emitted.
The energization activation process is processing which is performed for the electron emitting devices after the completion of energization forming processing. Specifically, the application of a predetermined pulse voltage is repeated under an environment having the degree of vacuum of about 1×10−2 Pa to 1×10−3 Pa in which an organic substance is present. Thus, carbon or a carbon compound is deposited on the electron emitting portion formed by the forming. Accordingly, an emission current from the above devices is markedly increased.
As described in JP 3087849 B described above, wirings for connecting between the plurality of electron emitting devices have a slight resistance value. Thus, when a large size matrix panel or the like is used, a wiring resistance cannot be neglected and the energization activation process is influenced thereby. Therefore, in JP 3087849 B, it is indicated that a voltage compensation method of applying voltages from column directional wirings to compensate the influence of voltage drop by row directional wirings is effective.
However, in the case of the above conventional technique, the following improvement is required.
As an electron source plate composed of a large number of electron emitting devices, there is given an electron source substrate having a simple matrix structure in which electron emitting devices are arranged in a matrix shape with, for example, M rows and N columns. When the above energization activation process is performed for such a substrate, a voltage is applied to a common wiring for M rows and N columns which is connected with device electrodes.
However, when the energization activation process is performed for the above electron source substrate having the simple matrix structure, there is the case where an unevenness in electron emitting characteristics is caused. As the causes, there are given a variation in activation gas atmosphere and the influence of a wiring resistance by a matrix wiring. The present inventor(s) have concentratedly studied a method of eliminating these causes.
As a result, when the influence of the variation in activation gas atmosphere is eliminated, it is found that a method of dividing the energization activation process into a plurality of processes of at least two stages to eliminate the influence of the activation gas atmosphere (described later in detail) is effective.
Also, when the influence of the wiring resistance by the matrix wiring is eliminated, it is found that an energization method of compensating the influence of voltage drop (described later in detail) is effective.
However, when the above method of eliminating the influence of the variation in activation gas atmosphere and the above method of eliminating the influence of the wiring resistance by the matrix wiring are simultaneously used, a further variation in electron emitting characteristics is caused. Thus, when these methods are simultaneously used for the method of canceling a variation in electron emitting characteristics, there is an insufficient point.
A matter to be solved by the present invention in the application is this point.